The present invention relates to an antiglare sheet for use with a display of a portable game machine adapted to lessen susceptibility of a user of the machine to visual dysfunction or ophthalmic anomaly, such as asthenopia, through affixment to the display.
Generally, when a worker is engaged in a visual work involving prolonged use of the eyes, he or she tends to suffer asthenopia.
Causes of asthenopia are classified into five categories: accommodative, myopathic, syndromic, aniseikonic, and neurogenic. However, a visual display terminal (VDT), such as a personal computer or TV has become a cause of asthenopia which does not definitively belong to any of these five categories.
Visual work with a VDT is said to involve visual dysfunction, such as fatigue of the eyes, visual disorder, dimming of vision, or eye pain; or ophthalmic anomaly, such as asthenopia, myopia, keratoconjunctivitis, increased tension of the eye, or lacrimal disorder. These symptoms are generically called VDT ophthalmopathy.
In order to prevent VDT ophthalmopatby, there has been devised a framed or film-type filter to be attached or affixed to a display screen of a desktop personal computer or to that of a TV. Such a filter shuts off a certain percentage of visible light emitted from a display and prevents reflection of external light in the display screen, to thereby improve contrast of a displayed image. When a display is of a cathode-ray-tube type, the filter removes radiation and ultraviolet rays emitted from the display.
However, such a filter for use with a display of a portable game machine has not been devised. Since the portable game machine is used both indoors and outdoors, the number of types of external light forming an image on the display screen increase. Examples of such external light include indoor lighting or sunlight. Further, since the portable game machine is often used while its display faces upward, the frequency at which external light forms an image on the display screen increases further.
Since a user plays a game with concentration while staring at the display screen of the portable game machine, reflection of an external-light source in the screen affects the eyes of, particularly, a preschooler or an elementary school student, who is in an important stage of physical development. Such an adverse effect on the eyes of children may cause an irreparable affection of their eyes. This is considered to be a kind of disease resulting from civilization, and has become a worldwide issue in relation to health of eyes.
The above problem may be solved through attachment of a frame-shaped filter to the display of a portable game machine or through bonding of a film-shaped filter to the display. However, attachment of a frame-shaped filter to the display impairs portability due to projection from the display. Further, in the case of a conventional film-shaped filter, since adhesive is applied to the entire surface of the filter, the filter is difficult to affix to the display screen through a manual operation. Also, the affixment involves entry of bubbles between the film and the screen, impairing visibility of the screen. Further, entrapped bubbles swell and expand with ambient temperature.
When an affixed film-type filter is removed from the display screen for replacement, the display screen is smeared with residual adhesive, impairing the function of a replacing filter. A similar problem arises when the same film-type filter is re-affixed; for example, after failure in an initial attempt at affixment.
In order to avoid the above problem, in manufacture of a display of a desktop apparatus, a film-type filter is mechanically affixed to the screen of the display for permanent affixment, thereby preventing entry of bubbles between the filter and the screen. However, when the filter is to be replaced due to deterioration, such as scratches, smudges of fingerprints, or discoloration caused by long-term use, the display itself must be sent to a repair shop. In the worst case, the display must be replaced.